The present invention relates generally to a metal cutting tool, and in particular, a metal cutting tool equipped for processing of workpieces by milling or drilling.
Metal cutting tools for processing workpieces by cutting are in use, which have a tool body with several cutting plates releasably fastened thereon. As a rule, the cutting plates can be exchanged and have a great degree of hardness and wear resistance. The tool body in turn holds and guides the cutting plates in appropriate plate seats. Often the cutting edges which are used for processing by cutting are intended to be of a length which is greater than the length of a single cutting plate. In this case the desired cutting edge is put together from the cutting edges of several cutting plates which are arranged on the tool body in such a way that each slightly overlaps the other in the circumferential direction.
In connection with peripheral milling cutters in particular, the cutting plates are arranged one behind the other on a helical line in several chip grooves. In this case the cutting plates arranged in successive chip grooves are offset in the axial direction in such a way that they add up to form a complete cutting edge. However, two chip grooves are then required for forming one single complete peripheral cutting edge.
It has also been attempted to arrange the chip grove in such a way that the cutting plates overlap each other. In this way it is possible to form a complete cutting edge with the cutting plates of one chip groove. If, for example, such a metal cutting tool has three chip grooves, it has three complete peripheral cutting edges. It is possible to achieve a large metal cutting output in this way. However, the resultant spiral angle defined by the cutting plates arranged one behind the other in the chip grove becomes relatively shallow. The spiral angle is that angle which the row of cutting plates forms together with the tool axis. The helix angle is defined as the angle which the row of cutting plates forms together with the peripheral direction. The helix angle is large (almost 90xc2x0). In some cases this is not desired. Moreover, the axial support of the cutting edges is complicated.
The design of continuous cutting edges at the tool end of drilling tools whose radius is greater than the length of an available cutting plate is even more complicated. If, for example, it is intended to provide two overlapping cutting plates at the tool end, the plate seats required for this result is a considerable weakening of the tool body. Tools with more than one end cutting edge (for example with four cutting plates for creating two end cutting edges) are almost impossible to produce.
Based on the foregoing, it is an object of the invention to provide a metal cutting tool which, with a simple design, makes a large metal cutting output possible.
A metal cutting tool in accordance with the invention has a tool body with plate seats which are arranged and designed in such a way that lateral side faces of adjoining cutting plates contact each other so that their cutting edges join each other without a break, or they overlap each other. The mutual contacting of the cutting plates provides a support for the cutting plates, and at the same time, a simple design of the plate seats. A respective adjoining cutting plate then takes on the function of the lateral or axial support of a cutting edge. Therefore no further support surface need be provided in the plate seat at the location of the respective plate seats. Because of this, the plate seats may have a particularly simple design. The plate seats require little space and result in only slight weakening the tool body. It is therefore possible in a simple way to arrange a comparatively large number of cutting plates at the tool end.
Furthermore, a relatively steep helix angle results from the direct contacting of the cutting plates in the axial direction, which is fixed by the row of the cutting plates in each chip groove. This is beneficial for the stability of the tool body, which is therefore weakened very little by the respective chip grooves. This also can be beneficial for the metal cutting output, either because the tool body can withstand large forces, or in that a particularly large number of chip grooves is provided on the tool body, which then result in a large number of teeth (number of cutting edges, i.e. number of complete cutting edges).
Moreover, the arrangement in accordance with the invention assures that the overlap of adjoining cutting edges is comparatively small. This results in an even chip thickness along each cutting edge. Thus, each point on the cutting edge of each cutting plate can be optimally loaded, i.e. neither overloaded nor insufficiently loaded, so that the productivity of the cutting plates can be maximally used.
The plate seats can have resting surfaces arranged at the same height so that the cutting edges of adjoining cutting plate directly rest against each other. However, there is the possible danger that chips become wedged between the cutting plates. This is prevented if the cutting plates overlap each other at least slightly. This can be achieved by the use of cutting plates of varied thickness, or even better by an offset of the resting surfaces of the plate seats with respect to each other in a direction at right angles with the resting surfaces (i.e., circumferential direction). If possible, the offset of the resting surfaces should however be less than the thickness of the cutting plates so that adjoining cutting plates can make contact for supporting each other. In this respect it is particularly preferred to limit the distance between the resting surfaces of adjoining plate seats at the outer circumference of the cutting tool to such a size that the cutting plates have sufficient contact also at their radially outside border. This also applies to radially adjoining cutting plates, here, also, it is either possible to operate with cutting plates of different thickness, or with offset resting surfaces, in order to achieve that the end cutting edges of the tool overlap.
It is considered to be advantageous to divide the lateral faces used for supporting the cutting plates into areas, one of which is used as a contact area. In the extreme case the contact area can take up the entire lateral face, particularly if the cutting plates are of different thickness. However, preferably the contact area only occupies a portion of the lateral face, in which case the contact area then is preferably oriented parallel with the corresponding lateral face of the adjoining cutting plate. This can be achieved in that the angle between the contact area and the front of the one cutting plate coincides with the angle between the lateral face and the base of the other cutting plate.
The resulting contact level between the cutting plates is preferably oriented at an angle with respect to the resting surface of the plate seat, which is other than a right angle. It is possible by means of this inclination of the contact level to achieve a slight overlap of adjoining cutting edges which is just large enough that the cut of the cutting edge of one cutting plate makes a transition without a shoulder into the cut of the cutting edge of the adjoining cutting plate.
An planar contact as well as a line contact can exist between the cutting plates. The planar contact is considered to be advantageous in view of the transmission of cutting forces acting on the cutting plate.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: